Skip the auto shop - Our mechanics make house calls

P0412 OBD-II Trouble Code: Secondary Air Injection System Switching Valve A Circuit Malfunction

check engine light logo

P0412 code definition

Secondary Air Injection System Switching Valve A Circuit Malfunction

What the P0412 code means

P0412 is an OBD-II generic code that the engine control module (ECM) got input from the air injection system driver that the air pump or air switching valve has malfunctioned with an open or short circuit.

What causes the P0412 code?

  • The air injection switching valve voltage is too high indicating an open circuit.

  • The air injection switching valve voltage is too low indicating an short circuit.

  • The ECM sets the code from diagnostic inputs from the air injection system driver.

What are the symptoms of the P0412 code?

  • The Check Engine Light will be illuminated and the code is set in ECM memory and freeze frame.

  • The air injection system pump may not come on.

  • The engine may not have any drive symptoms except a check engine light is on.

How does a mechanic diagnose the P0412 code?

  • Scans codes and documents the freeze frame data in order to verify the problem

  • Clears the engine codes retest the air injection system for proper operation

  • Tests the air injection switching valve is controlling the air injection pump operation during tests

  • Checks the resistance of the air injection pump and air injection switching valve

  • Checks the air injection pump for proper voltage between the pins of power and ground

Common mistakes when diagnosing the P0412 code

  • Not checking for proper battery voltage above 8 volts to the air injection pump before replacing the pump for no air pumping out of it

  • Not checking the air injection pump power relay for burnt wire connections before replacing a bad air injection pump or air switching valve

How serious is the P0412 code?

  • The air injection pump system is to help lower the emissions coming out the exhaust and can cause the vehicle to fail emission testing.

  • The Check Engine Light being on causes the vehicle to fail emission testing.

  • The air injection pump should not cause any drive symptoms other than a Check Engine Light.

What repairs can fix the P0412 code?

  • Replacing the air injection pump and power relay
  • Replacing the air injection switch valve
  • Repairing the wiring to the air injection pump power relay connection

Additional comments for consideration regarding the P0412 code

Code P0412 is a problem with the air injection system driver in the ECM cannot turn on the air pump to test it during startup. A shorted air injection pump circuit can short out the air injection driver in the ECM and should be considered when diagnosing the problem.

Need help with a P0412 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.


Post a question and get free advice from our certified mechanics.


More related articles

Symptoms of a Bad or Failing Flexible Clutch Hose
Common signs include difficulty shifting, low clutch fluid, and feeling no resistance at the clutch pedal.
P0121 OBD-II Trouble Code: TPS "A" Circuit Range Performance Problem
P0121 code definition Throttle Pedal Position Sensor/Switch (TPS) A Circuit Range Performance Problem What the P0121 code means P0121 is a generic OBD-II code which indicates that the Engine Control...
How to Buy Fuel Treatments
Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine,...

Related questions

Q: Car revs high

Air leaks into the intake system (a loose hose, or the EVAP valve as you have already experienced). If there are no codes, even transient codes which may not set the Check Engine Light, the problem could be a loose...

Q: Engine misfiring.

A misfire can be caused by a lot of things, from a worn spark plug to an internal engine problem. The first step is to retrieve the diagnostic codes associated with the check engine light. These codes will provide a...

Q: 4WD will not engage

First, if there are any other lights on the dash, (such as the VSC, ABS etc.,) the 4WD module may not allow the 4WD to engage. As for the symptoms that could be causing this condition, it could be: ...